Method of starting up a boiler



Jan. 14, 1964 S. S. BO WLUS METHOD OF STARTING UP A BOILER 3 Sheets-Sheet 1 .Original Filed Feb. 18. 1957" INVENTOR Sanford S. Bowlus 3 Sheets-Sheet 2 INVENTOR Jan. 14, 1964 s. s. BowLus METHOD OF STARTING UP A BOILER Original Filed Feb. 18. 1957 Sonford S. Bowlus e 2 M ;mi %id Jan. 14, 1964 s. s. BOWLUS 3,

METHOD OF STARTING UP A BO'ILER Original Filed Feb. s 1957 i 3 Sheets-Sheet 3 55 se g sa g F ig .4. 5! W i 53 INVENTOR 54 Sunford S. Bowlus United States Patent O &117556 METEO@ OF STARTNG UP A EOILER Senior& S. Bowins, Erie, Pa., assignor to Bla'. -Knox Company, Pittshnrh, Pa., a eo'poration of Delaware Continnation of appiication Ser. No, i9,594, Apr. 4, 1963, whieh is a eontinnation of appication Ser. N ?88,642, lan. 13, 1953, which is a division of appliea tion Ser. No. 6485641, Feb. 18, 1957. This appiication Dec. 28, lil, Ser. No. 79,629

3 Claims. (Ci. 122-4) This invention relates to a method of starting up a boiler, and particularly a method involving traversing a zone in the boiler with a sensing element detecting the local condition of the hot gases along the path of movement of the sensing element and utilizing the informa tion thus obtained in control of the boiler during the starting up period. This application is a continuation of my co ending application Serial No. 19,594, filed April 4, 1960, now abandoned, which in turn is a continuation of my application Serial No. 708,()42, filed `lanuary 13, 1958, now abandoned which in turn is a division of my application Serial No. 64(),641, filed February 18, 1957, now abandoned.

While in its broader aspects my invention is applicabie to the scanning of furnaces of various types for various specific purposes my invention has especial utility when employed in connection with the starting up of a steam boiler and will be so described herein.

A convcntional steam boiler has tubes and a superheater arranged in well known manner and means for firing the hoiler such as a stoker or hurncrs which when operation cause hot gases to traverse the boiler in thermoconductive relation to the tubes and the superheater. The hot gases generated by the stolter or burners may first traverse tubes in the furnace charnber constitu ing the portion of the boiler known as the evaporator.

he superheater for snperheating steam beyond the evaporator may be disposed at the upper portion of the furnace chamber in the path of the hot gases as they move generally upwardly in leaving the evaporator. The gases may then pass to a stack and may impart heat to economizers en route to the stack as well known to those skilled in the art.

The evaporator is maintained full of water or other liquid being evaporated which etlectively cools it to about the boiling point of the liquid at the pressure maintained, but the snperheater contains only vapor, which is not an effective coolant, especially when vapor is not being withdrawn from the superheater as is the case when the h r is being started up.

i urthermore, when the boiler is being started up and while no vapor is being withdrawn, substantially all the heat of combustion is being used to increase the temperature of the boiler setting, the evaporator and the superheater. t is important in relation to the life of the boiler and efiicient operation thereot to bring the boiier gradualiy to its proper Operating conditions Without forming hot Spots therein. Unlike the condition obtaining in non-nal operation, the heat released by the fuel is not principally absorbed by the evaporator at substantially a constant equilibrium temperature, and the temperature may rise to an exeessive degree at one or more portions of the boiier and may result in damage, particularly to the superheater. The furnace chamber is of substantial Width transversely of the direction of flow of the hot gases and absorbs heat unequally at different transverse portions thereof during start-up. The gases are not homogeneous across the furnace but vary in temperature and composition in streams flowing through the furnace.

For the practice of my invention I install furnace scanning apparatus in the furnace at or close to the superheater, preferably in the zone adjacent the evaporator but ahead (or tip-stream) of the superheater. I preferably provide for traversing the Zone adjacent the entrance to the superheater with a sensing element detecting a local condition of the hot gases along the path of movement of the sensing element. The stoker or burners is or are adjusted in response to the local condition so detected, bringing the nrnace into proper Operating condition. By scanning the gases from side to side local hot streams may be detected and the firing adjusted so that there will be no local hot spot endangering the superheater, which is without the protection of any cool ing means.

My furnace scanning apparatus is, as above indicated, for detecting a condition in the furnace chamber. The condition ma for example, be temperature, or it may be the composition of the gases. In its broader aspects my invention is not limited with respect to what particular condition is detected, but for purposes of explanation and illustration my invention will be described in connection with furnace scanning apparatus for detecting the temperature across a fnrnace chamber.

I provide a method of starting up a boiler having tubes and a superheater and having firing means in the lower part of the boiler comprising initiating operation of the ring means, causing hot gases to traverse the boiler between opposed Walls of the boiler in thernoconductive relation to the tubes and the superheater, moving across the boiler in a direction generally from one of said walls toward the other thereof, a sensing element detecting at each increment of such movement of the sensing element the local condition of the hot gases along the path of movement of the sensing element and in so doing traversing the hot gases in the region of the superheater with the sensing element and simultaneously detecting the location of the sensing element and adjusting the firing means in response to the local condition so detected. The condition detected may, for example, be temperature, or gas composition. The sensing element may and in certain cases preferably does traverse a zone adjacent the entrance of hot gases into the superheater.

The firing means may comprse bnrners arranged to fire inwardly into the lower part of the boiler or ranged across the boiler. Operation of less than all of the burners may be initiated. The hot gases may traverse the zone adjacent the entrance to the superheater and the sensing element may detect the local temperature or other condition of the hot gases along the path of movement of the sensing element, and the burners may be adjusted in response to the local temperature or other condition so detected. The sensing element in its continued traversing of the hot gases detects Variations in the temperature or other condition of the gases as the burners are adjnsted and the burners are readjusted from time to time in response to such variations While the boiler is being started.

To determine the composition of the furnace gases, a sampling tube may be mounted adjacent the hot junetion of the probe connected through a hose and reel, simila' to that provided for coolant, to a conventional gas analyzing device. Thus both the temperature and composition of the gas across the furnace may be deterrnined together, the probe sensing substantiaily the complete condition of the furnace gases as the probe traverses the furnace.

Other details, objects and advantages of the invention Will become apparent as the following description of a present preferred method of practicing the same and apparatus which may be used in practicing the same proceeds.

In the accomparying drawings I have illustrated a present preferred method of practicing the same and have &1173556 3 shown apparatus which may be used in practicing the same in which:

FIGURE l is a diagrammatic vertical cross-sectional View through a stearn'boiler;

FIGURE 2 is a diagrammatic elevational View, partly in vertical cross section, of furnace scanning apparatus applied to the stearn boiier;

FIGURE 3 is a wiring diagram illustrating one wiring system which may be erneloyed for Operating the fornace scannig apparatus; and

FGURE 4 is a fragnentary wiring diagram illustraiing he wiring 'for the means for determining the position of the probe in -the furnace chamber.

Referring now more particularly to the drawings, FIG- URE 1 shows more or less diagrammaticaliy a boiler comprising a vertically disposed furnace 2 of generally rectangular horizontal cross section having side walls 3 of refractory material at the inside surfaces of which are provided generally vertically disposed tubes 4 through which the water or other liquid to be evaporated is adapted to flow. The tubes 4 communicate with a header 5 forming a closed horizontal loop 'at the bottom and a header 6 forming a closed horizontal loop at the top. The headers 5 and 6 communicate through tubes '7 and 3 respectiveiy with a drum 9 so that Water is recirculated in the directions of the arrows o in FE URE 1 and steain is withdrawn from the top of the drum 9 through tubes to and passes in the direction of the arrow b to a superheater 11. The superheater is shown in FIGURE 1 in Outline defining the area in which it is installed without showing the banks of the tube of which it is comprised, it being understood `that the superheater is of conventional construction. It is located in the path of 'the gases generally beyond the evaporating or stearn generating section of the boiler.

in FIGURE 1 the firing means selected for illustration comprises burners set in the furnace wall -bnt it is *to be understood that any other conventional ring means such as mechancal stokers may be provided.

At their lower portions the wails 3 are provided with refractory lined burner openings 1:2 'through each of which a burner 13 is adapted to discharge -its flarne Vinwardly. The burners are shown only diagramniaticaliy oecause they may be of conventional Construction and supplied with fuel and air for combustion as well :known to those skiiled in the art. The burners may be ranged in series 'both verticaily and *horizontally and :thus .are arranged as shown in FGURE 1 in any desired firing pattern, as at the four corners for tangential fiarne projection or in horizontal rows in opposite walls for Opposed-bank firing. FIGURE 1 indicates a vertical series of four such tangential or opposed-bank sets of burners along the walls 3 which-would fire inwardly into the furnace. in tangential firing the burners 13 fire at an angle 'to the walls 3 so as to proect their flames on a `tangent to an imaginary circle about the vertical axis of the furnace, while in opposed-bank firing-the burners project their flames -substantially perpendicular to the furnace walis 3, both arrangements being well known and conventional'in the art.

The burners '1% as shown are located in the lower part of the boiler and generate hot combustion gases which pass upwardly through the boiler including *the superheater fil and out through a duet 14 in which are disposed economizers 15 which may be of conventional Construction to a stact, not shown, through which the gases 'are discharged to the atmosphere. The path of the gases is indicated by arrows c in FIGURE 1. The superhented stearn is delivered from the superheater 11 though a ppe 16 in the direction of the arrow d in FIGURE l. The header e and superheater 11 are surrounded by a re'ractory containing structure designated generally by reference numerai 17 which is integral and continuous with the furnacc comprising the walls 3 and also with the duet 14. Thus continuous flow of hot gases as indicated by arrows c is provided for. The portions of the tubes 4 in the lower part and the middle part of the furnace constitute the evaporating or stearn generating portion of the boiler. A bathe 18 partially constricts the upper part of the furnace and Controls the flow of gases to the superheater as shown in FIGURE 1. Solid residue such as slag is removed at the bottom through the cone 9.

The furnace scanning apparatus or probe is adapted to extend through one of the walls of the boiler comprising the furnace so as to scan the furnace chamber generally horizontally in a direction parallel to the walls 3. The prob-e is designated generally by reference numeral 2@ (see FIGURES 1 and 2) and passes through an opening 21 in a wall 22 of the boiler. The probe is adapted .to sean or traverse the furnace chamber in the region of or close .tothe superheater, preterably adjacent the entry portion of the superheater 11 as shown in FIG- URE 1. It detects and indicates the condition of the furnace gases as they 'enter the superheater. The probe may be somewhat within the general superheater area as shown in FIGURE 1 or -it 'rnay be outside thatarea, but for most sensitive control it is preferably installed adjacent the point where -the hot -gases enter the superheater. As .pointed out above, 'the probe detects a condition in the turnace chamber at points along its path as it Scans or traverses the furnace chamber and -the burners are adjusted .intresponse to the condition or conditions detected by the probe so that .the boiler operates efiiciently and without producing unduly overheated zones which rnay be detrimental to the tubes, the refractories or other portionstor" the installation.

Referring to FIGURE 2, an elongated support shown as :in the form .of an Lbeam 23 is -rnounted outside the furnace charnber adjacent .the opening 21 in the wall 22. One end of the I-beain may be supported from the wall by a bracket 24 as shown in FIGURE 2 and othcr sutable supporting means, 'not shown, for the I-bearn may be provided. The I-beam 23 provides a straight horizontal track perpend-icular to the wall ZZand directly above the opening 21. A cariage 25 is supported by the I-beam 23 through rollers 26 journaled .in u-pward extensions 27 of 'the carriage, the rollers being disposed .atop the respective bottom flanges of the Lbeam. Thus the carriage 25 .is `adapted to move horizontally parallel to the I-beam and supported by the I-bearn by the rollers 26 which 'are rnoun-ted .for free rotation and turn as the carriage moves. The ,path of the .carriage is perpendicular to the wall 22 and in alignment with-the opening 21.

connected with the .carriage 25 and extending to the left therefrom viewing FIGU-RE 2 are concentric outer .and inner conduits or tubes 28 .and 29 respectively. The

tubes 28 and 29 are in etfect integral and spaced apart by suitable spacing means not shown to provide an annular space 30 therebetween. Within the inner tube 29 is disposed a themnocouple 3 1 which may be of conventional Construction, comprising, for example, wires of dissimilar metal joined together at -an end of the therrnocouple forming the so-called hot junction designated by reference numeral 32. The hot junot ion 32 .of the thermocouple projects out of the end of the tube 30` and also out of ;the end of the tube 23 through a fitting 33 which seals the ends of the tubes about the thenmocouple. The

opposite ends of the wires of dissimilar metale forming' the thermocouple are disposed within the carriage 25 where they are respectively connected by wires with a voltrneter 34 which is mounted on the instrument panel in the boiler rooin. The connections to the voltmeter are shown purely diagrammatically in FIGURE 2, comprising a spring cord 35 and an electrical conduit 36. Each of the spring cord '35 and the electrical conduit 36 comprises two separate conductors. The conduotors in the spring cord 35 are connected at one end with the hot junction wires of the thermocouple within the carriage 25 and are connected at the other end with conductors in the electrical Conduit 36 which in turn is connected with the terminals of the voltmeter 34. Thus the cold junction of the thermocouple is at the voltmeter and the respective wires of dissirnilar metals of the thermocouple are eleotrically connected with the terminals of the Voltmeter 34. A dilerence in temperature between the hot and cold junctions of the thermocouole produces an electrical potential or voltage therebetween which is measurable by the voltmeter. The voltage thus produced is proportional to the difference in temperature between the hot and cold junctons of the therniocouple, Tnus the reading of the voltmeter 34 is a measure of the temperature at the hot junotion 32 of the thermocouple, since the temperature at the cold junction of the thermocouple at the control panel is substantially constant. The voltmeter 34 may be calibrated in degrees of temperature.

Mounted on the l-'beam 23 near the end of the l-beam which is relatively adjacent the furnace is an electric motor 37 which through reduction gearing 33 drives a sprocket 39. The motor 37 is of the reversing type. Adjacent the opposite end of the l-beam 23 is a bracket 4% which carries a sprocket 41 which is coplanar with the sprooket 39. A sprocket chain designated by the chain line 42 is dead-ended to the carriage 25 at each end of the sprocl'et chain as indicated at 43 -and passes about ti e sprockets 39 and 41 so that the reach of the sprocket chain which is behind the carriage 43 viewing 'FlGU RE 2 extends continuously between the sprockets 39 and 41. ?aotation of the motor causes movement of the carriage along the l-beam through the action of the sprocket chain 42. The outer `tube 28 is guided between rollers 44 so that the probe passes freely through the opening 21.

Coolant is adapted to be supplied to the annular space 35 between the tubes 23 and 2-9. The coolant may be compressed' air which is supplied from a suitable source through a valve 45 to the hollow trnnnion 4:6 of a reel 47. The hollow trunnion 46 communicates with a hose which is wound upon the reel 47 and leads to the carriage 25 where it COIlL''llIllCtS with the annular space 3 between the tubes 28 and 29. Adjacent its left-hand end viewing FIGURE 2 the tube 28` is provided with lateral openings 49 through which the coolant escapes. The reel 37 is spring operated to reel up the hose 43 which the carriage 25 moves toward the right viewing FlG'Ll?` 2 and to pay out the hose when the carriage moves toward the left. The spring cord 35 similarly contracts when the carriage moves toward the bracket l and stretches out when the carriage moves toward the left away from that bracket.

Carried by the shalt which carries the sprocket 41 is a potenti meter which is electrically connected through an electri-c l Conduit 5-1 with a position indicator in the for" of a voltmeter 52 (see FGURES 2 and 4). The current for the potentiometer is supplied through leads 53, a rheosiat eing provided for zero adjustment of the potentiometer. The movable potentiometer contact is operated when the carriage 25 moves along the l-beam 2-3 consequently when the hot junction 32 of the thermocouple traverses its path in the furnace chanber. result is a change in voltage which can be read on the voltmeter 52. That voltrneter thus determines the position of the hot jnnction of the thermocouple at all times. The voltmeter 52 may be calibrated direc ly for the position of the hot junction of the thermocouple. Ths the two instruments 34 and 52 make it possible to determine thetemperature at each point along the path of travel of the hot junction of the thermocouple in the furnace chamber since the temperature at each instant is shown by the instrument 34- and the position of the hot junction of the thermocouple at each instant is shown by the instrument 52.

switches SS, 56, 57 and 58 are provided along the path of the carriage and are adapted to be operated by a finger or lug 59- projecting upwardly from the carriage.

The control mechanism will now be described with particular reference to FIGURE 3. The motor 37 is shown at the lower left-hand corner of the figure. lt is `a three-phase motor and openates in either direction, being reversed by reversing any two of the three electrieal connectio ns to the motor. The switches 55, 57 and 53 `are shown at the bottom of FlGURE 3. The switch 55 is a limit switch :at the extended or farthest inward position of the probe. When the limit switch 55 is operated by the finge'r on the carriage 25 it opens one contact and closes another. The switch 56 is a limit switch at the retracted or farthest outward position of the probe. When the limit switch 56 is o erated by the finger 59 on the oarriage 25 it opens one contact and closes another. The switch 57 is for controlling the va'lve 4 5 through a solenoid se. The valve as above explained contro-is the admission of cool ant to the hose 48. The switch 57 -is :a sustaining contact single pole switch open and closed by the finger 59; in other words, the switch 57 closed except when the carriage moves to the right viewing FIGURE 2 so that the switch is opened by the finger 59. When the carriage moves back to the left viewing FIGURE 2 the switch 57 is again closed. The switch 58 is -a limit switch at the parked position of the cani-age. lt contains two normally closed Contacts which open when the (marriage reaches parked position. A stignal `device is shown at 61. The signal devioe may be for making an audible or visual signal or both being shown as a 'bell or gong.

There is shown at 62 a solenoid openated relay with two normally open Contacts 63-54 and 65-66, both of which close w en the solenoid is energized. There is shown at 67 a solenoid oper-ated rel ay with two normally open Contacts 68-@ and iii-"ll which close when the solenoid is energized. There is shown at '72, a solenoid operated relay with two normally open Contacts 73-74 and 75-76 and two normally closed Contacts 77-78 and Reference numeral %l designates generaltly a reversing switch which operates selectively by means of solenoids 32 and 83 to close the `tJhree-phase motor circuit in forward or reverse connections to the motor 37. Solenoids 82 and 223` are not connected in the threephase circuit but are wired in a single phase control cir- 'cuit in which :the auxiliary Contacts presently to be described operated by the same solenoids rare -also connected.

At the right of FIGURE 3 is shown a four-button push button station, all of the buttons being of the mom-entary contact type for return to normal position when the operator removes his finger from the button. The button to ex tend the probe is designated and has one nor mally closed contact ss se and two normally open contacts 37-8$ and 89 90. The button to retract the probe is designate d and has `one normally closed contact lE-93 and two norm aly open Contacts Q i-95 *and -97. The button to stop the probe is designated 9% and -lias one normally closed contact fill-dilli. The button to park the prcbe is designated 101 and has one normally open contact 102-103.

Assum-ing that the solenoid of the :relay 72 is not energized and that the contacts '77-78 are therefore closed, pressing either the eXte-nd button 34 or the retnact button 91 momentarily closes the circuit from the line 1-1 through contests 37-88 or l-95, as the case may be, and the normally closed Contacts 77-78 to the solcnoid of the relay 62. 'This causes the contacts 63-54 in the relay 62 itself to close 'and thereby electrically latches the relay 62 in position with its solenoid energized through the normally closed contacts %El-1%@ of 'dhe stop button 93. T he relay 62 also closes contacts 65-66 connecting the line L-ll to both terminal 1% of the limit switch 55 and the terminal %5 of the li t switch 56, which condition will be maintained url-tii such time as the solenoid of the relay 62 is de-energized as would occur upon pressing the stop button 93. The solenoids 82 and 33 of the reversing switch Bl are connected in circuits between the limit switches 55 and 56 and the opposite line L-Z. The

&1173556 7 solenoid 32 controls normally open contacts 169-113 and normally closed contacts 197-il3. The solenoid 83 controls norin aly open contacts 1 1 l-llz and normally closed co ntacts 123-129. In the crcuit to solenoid 32 is a normally open contact 89-99 of the extend push button and in like manncr in the crcuit to the solenoid '33 is a normally open contact 96-97 of the retract push button 91, These Contacts are also solectively closed as either of the push buttons 84 and 91 is pressed whereby to nomentarily selective ly energize one or the other or" the solenoids 82 and 83 as the case may be through the various other Contacts closed at that time. in the crcuit conta ning the solenoid 3 2 these `are the normally closed Contacts 123-129 which would be opened by the solenoid 33, Contacts 3-30 of the relay 72, Contacts i lim-186 of the limit switch 55 and -contacts 92-?3 in the retract button 91. Similarly, in the crcuit containing the solenoid 83 .these are the normally closed contacts "im -1% which would be opened by the solenoid 82, contacts 35-36 in the button 34, contacts 119-126 in limit switch S and contacts 104-165 of limit switch 55. As soon as either of the solenoids 82 and '33 is energized it oloses a Shunt crcuit (lihi-11@ in crcuit with the solenoid 82 and ill-112 in the crcuit with the solenoid 83) around the push button contact and thus electrical'ly latches itself in energized position, permitting release of the push button. When one of the solenoids 82 and 33 is thus energized it closes its respective contacts 313 to the motor which is thereby cause to start in one direction and to continue to run in the same direction 'until stopped or reversed as Will presently be described. T-hus if the stop button 93 should be pressed, opening Contacts Q'Q-'tl fi* and thereby de-energzing the solenoid of the relay 62, that relay will return to its normal position breaking the contacts %ES-66 to both of the limit switches and 56 thcreby de-energizing either of the solenoids 32 and 33 and closing all three-phase circuits to the motor 37. Each of the eXtend push button .S i and the retract push button 91 has one normally c-losed contact in addition to the tw-o normally open Contacts to which reference has been made above. Those normally closed contacts are wired in the circuits between the limit switches 55 and 56 to the reversing switch solenoids. so as to open whichever of those circuits rnay have been closed when the other crcuit is closed by pressing that particular button. Thus the normally closed contacts '92-93 of the retract button 91 `are in series between the limit switch 55 and solenoid '82 while the normally closed Contacts 85-86 of the extend 'button 34- are in series between the limit switch 56 and the solenoid 83; Thiis thme push buttons provide manual control of reversal of the motor at any time.

When the movement of the carri age has been started as above described and the can'iage moves to the position in which the finger 59 engages one of the limit switches 55- and 56, that limit switch opens its normally closed contacts (104 -7166 of limit switch 55 or 1195- 114 of'l imit switch 56) and thereby de-energizes the solenoid 82 or the solenoid 83 as the case may be. This in turn oauses current to cease to flow to 'the motor 37. At substantially the same time the normally open contact (194-415 of limit switch '55 or 1875-1 26 of the limit switch 55) is momentarily closed. As shown in FIGURE 3 these contacts are connected in arallel With the contacts 89-96 of the extend 'button 84 and 95-97 of the retnact button 91 providing for manual control or reversal of the carriage, so that the operation of the limit switches has the same efiect and energizes the other solenoid (82 or 93 as the case may be) of the reversin g switch 81 'to reserve flow of current to the motor. The first eliect of reversal of flow of current to the motor is, of course, to slow it down and bring it to a quick stop, whereafter the motor mrs in the opposite direction. This stopping and reversal or" the motor is to be effected within a very short distance in the travel oi the carriage. The

e whole reversal takes place substantially at .the location of the limit switch or 56 as the case may be, the carriage not traveling through the limit switch in normal operation. Thus when the apparatus has been set in motion by pressing either the extend button 84 or retract button 91 the carriage is set in motiton in a certain direction and travels toward the opposite limit switch which automatically reverses it, this back and forth motion continuing and causing the probe to traverse and retraverse the furnace chamber until it is stopped in some way.

When it is desired to shut down the operation of the furnace scanning apparatus the park position button 101 is presscd. This momentarily closes the Contacts 107- ldfv in direct crcuit between the line L-l and the solenoid of the relay 73, .the opposite pole of which solenod is connected to the 'line 'L-2, When the solenoid of the relay 72 :is energized it closes contacts 73-74 in series through Contacts 117-118 in limit switch .58 to the line 'L-l and thereby l-atches itself in energized position. At the same time .Contacts 75-76 in relay 72 are closed, directly energizing the crcuit tothe solenoid %3 through the normally closed contacts 119-120 in the limit switch 58, '35-86 in the extend button 84 and 187-188 in the reversing switch l which are .closed only when the solenoid 32 is de-energized. At the same time normally closed Contacts 77-78 and 79-80 in relay 72 are opened which dc-energize the s-olenoid of relay 62 and opens the Contacts -66. It will be seen that if at the time the park button 161 is pressed and all this takes place the probe should be moving in the extend direction its travel will be reversed, while if the probe happens to be moving in the retract direction its travel will continue in the same direction under control of the crcuit which is changed as has been described. However, the limit switch 56 is no longer in crcuit .to the solenoid 83 but instead the limit switch 53 through the normally closed contacts 119-120 will control the point in the travel of the carriage at which the solenoid 33 will be de-energized. 'Therefore the retrac-tion of the probc will continue until the detent 59 on the .carriage 25 engages the limit switch 5 8. not only opens the Contacts 119-120' as has been mentioned but also opens the contacts 117-118 in crcuit to the solenoid .of the relay '72, causing the latter to be de-energized, which again restores Contacts 77 73 to their normally closed condition, which was the condition assumed at the beginning of this description.

'If at any time the temperature detected and indicatcd by the indic-ator 34 should be excessive, as, for example, more than l000 F., or whatever is considered a hazardous tempenature condition under the circumstances, the Contacts 121-122 in the temperature indicator will close and this completes a crcuit from the line L-l to the solenoid of the relay 67, closing contacts oli- 69 and contacts 7t-71. The contacts 68-69 are connected in parallel with the vcont acts ldi- 1613 of the park position button 191 so thatit they are closed the same Operations are effected `as described above when the park push button is pressed and the temperature probe is withdrawn automatically to parked position. Closing the Contacts -71 in the relay 67' completes the crcuit from the line L-l to the terminal 123 of the alarm devicc. The opposite terminal 124` of the alarm device is connected to the line L-Z. Hence the alarm will be actuated when the solenoid of the relay 67 is energized.

For control of the supply of cooling air to the probe the valve t is operatori by the solenoid 68; The single pole sustaining contact type switch 57 is mounted between the limit switches 56 and 58 in the path of the finger 59 so as to 'be tripped by that finger as the carriage passes the switch 57. This switch contains the Contacts 125-126 which are closed by travel of the carriage as it moves in the `eXtend direction and are opened by the carriage as it moves in the retract direction toward parked position. When the carriage is extended and `the contacts 125-126 are closed a circuit is completed to the solenoid t), thereby opening the valve 45 and admitting air to the hose 48. As the carriage is rctracted to parked position the Contacts- 125-126 are opened and the solenoid 65' is de-energzed, shutting ofi the supply of air. The switch 57 is mounted -on the I-heam 23 in a position which will shut off the flow of air as the probe is retracted but before it has been entirely removed from the fumace and has entered `the wall box 127 (see FIG- URE 2).

While I have iliustrated a present preferred method of practicing the invention and have shown apparatus which may be used in practicing the same it is to be distinctly understood that the invention is not limited thereto but may be otherwise vaiously practiced within the scope or" the following claims.

I claim:

1. A method of starting up a boiler 'having tubes and a superheater and having ring means in the lower part of the boiler cornprisin g initiating operation of the firing means, causing hot gases to traverse the boiler between opposed walls of the boiler in thermoconductive relation to the tubes and the superheater, moving across the boiler in a direction generally from one of said walls toward the other thereof a sensing element detecting continuously at all points in the path of movement of the sensing element vin the space across the boiler between said walls the local condition of the hot gases and simultaneously detecting the location of the sensing element, evidencing at a single point on the instrument panel in the boiler room the location of the moving sensing element at each moment as the sensing element 'moves 'across the boiler and evidencing at 'a point adjacent the first mentioned point on the instrument panel in the boiler room the local condition of the hot gases at each location evidenced at the same moment at said single point and adjusting the firing means in response to the loca-1 condition `so detected.

2. The method of claim 1 in which the sensing element detects the local tempehatures of the hot gases and the firing means are adjusted in response to the temperatures so detected.

3. The method of claim 1 in which the sensing element traverses a zone adjacent the entrance of hot ases into the superheater and detects temperature variations in said zone and the firing means are adjusted in response to the variations in temperature thus detected.

References Cted in the file of this patent UNITED STATES PATENTS Knoblauch Dec. 1, 1942 OTHER REFERENCES Falkner, Quick-Starting of Large High-Pressure High- Teniperature Boilers," ASME Transactions, November 1953, pages 1407-1460. See pages 1407-1424 in particular.

Steam, Its Generation and Use, 'Dhe B-abcock & Wilcox Co., New York, N.Y 1955, 37th ed., 3rd printing, pages 6-18, 6-19, and 6-20.

Ste-am, Its Generation and Use, The Babcock & Wilcox Co., New York, NY., 1955, 37th ed., 3rd printing, pages 21-1, 21-2 and 21-3.

Power, January 1955, Volume 99, number 1, published by McGraw-Hill, New York, pages 16 and 17 relied on.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No@ 3,ll755 January ll 1964 Sanford S, Bowlus It is hereby Certified that error appears in the above number-ed patent requiring correction and that the said Letters Patent should read as correc ted below column 3, line 31 for of the tube" read of tubes column 6, line 53 for `*'normaly' read normally line 69 after "both" insert the column line 29 for "cause" read caused line 9 for 93 read 83 line 70 for "reserve' read reverse column 8 line for- "motiton' read motion Signed and sealed this 14th day of July 1964o (SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting officer Commi'ssioner of Patents 

1. A METHOD OF STARTING UP A BOILER HAVING TUBES AND A SUPERHEATER AND HAVING FIRING MEANS IN THE LOWER PART OF THE BOILER COMPRISING INITIATING OPERATION OF THE FIRING MEANS, CAUSING HOT GASES TO TRAVERSE THE BOILER BETWEEN OPPOSED WALLS OF THE BOILER IN THERMOCONDUCTIVE RELATION TO THE TUBES AND THE SUPERHEATER, MOVING ACROSS THE BOILER IN A DIRECTION GENERALLY FROM ONE OF SAID WALLS TOWARD THE OTHER THEREOF A SENSING ELEMENT DETECTING CONTINUOUSLY AT ALL POINTS IN THE PATH OF MOVEMENT OF THE SENSING ELEMENT IN THE SPACE ACROSS THE BOILER BETWEEN SAID WALLS THE LOCAL CONDITION OF THE HOT GASES AND SIMULTANEOUSLY DETECTING THE LOCATION OF THE SENSING ELEMENT, EVIDENCING AT A SINGLE POINT ON THE INSTRUMENT PANEL IN THE 